Water treatment devices are well known in the art. Such devices are employed directly in a water system, either in-line or at a terminal end, or in self-contained batch systems. An example of an in-line system is an under the counter device which filters water prior to reaching the faucet. Terminal end devices include counter top and faucet mounted filtration systems. Self-contained batch systems include devices such as carafe units.
Typical water treatment devices employ mechanical filtration or chemical treatment. Mechanical filters treat water by preventing passage of particulates. As a mechanical filter approaches the end of its useful life, restricted flow due to particulate accumulation provides a ready indication that element replacement is necessary.
Chemical treatment (e.g., activated carbon-based and ion exchange media) employs processes such as adsorption and ion exchange for removing undesirable chemical species. A major drawback associated with chemical treatment is that the chemical media eventually becomes inactive, providing no such indication that the useful life of the chemical element has been exceeded.
As a result, various methods have been employed to indicate end of life to the user where it is not inherently provided by the behavior of the filter media. Illustrative is the method disclosed in U.S. Pat. No. 4,686,037. In the noted method, the user compares the color of the pre-filter with a reference strip to determine when the media requires replacement. The problem with this method, however, is that it is inherently subjective and, therefore, subject to error.
A more accurate means of indicating end of useful life of conventional treatment units is through devices which use a process commonly referred to as "flow totalization". These devices totalize the liquid volume which is passed through the treatment media.
Both electrical and mechanical "flow totalization" devices are known in the art. Illustrative are the devices disclosed in U.S. Pat. Nos. 4,918,426; 5,089,144; 4,681,677; and 5,536,394.
In U.S. Pat. Nos. 4,918,426 and 5,089,144 electrical flow totalization devices are disclosed which employ pressure transducers. The transducers include integrated outputs to calculate total volume. After a predetermined volume has been reached, a valve is electrically actuated to stop flow.
U.S. Pat. No. 4,681,677 discloses a mechanical flow totalization device which employs a turbine interconnected with a series of gears. The gears are designed and adapted to mechanically "add up" the volume of water passed through the device. The gears also cooperate with a valve that is adapted to stop flow after a predetermined volume of water has passed through the device.
In U.S. Pat. No. 5,536,394 a mechanical flow totalization device is disclosed which employs a float mechanism. The float is designed and adapted to rotate a pre-determined distance upon each fill cycle of the water treatment unit. Once the float has made a specific number of rotations and has traveled a complete distance across a support rod, the float rests in a position where it visible through an opening in a housing, indicative of the end of life of the water treatment unit.
Although flow totalization devices address the end of life problem(s), there are drawbacks. One major drawback is that flow totalization devices are often complex and, hence, expensive. Another drawback is that such devices can, and in many instances will, adversely effect the flow thru characteristics of the water treatment device (i.e. filter cartridge).
An additional drawback with mechanical flow totalization devices is that the devices are typically incorporated into the replaceable cartridge. This approach is unnecessarily wasteful and expensive.
It is therefore an object of the present invention to provide a device for indicating the end of useful life of a water treatment system that is mechanically simple, accurate and reliable.
It is another object of the invention to provide a device for indicating the end of useful life of a water treatment system which can be readily reset upon replacement of the cartridge and/or chemical media.
It is another object of the invention to provide a device for indicating the end of useful life which enhances the flow thru characteristics of the filter cartridge.
It is yet another object of the invention to provide a device for indicating the end of useful life which is readily adaptable to various batch water treatment systems.
These and other objects of the present invention will be apparent to those skilled in the art from the following detailed description of the invention and the accompanying drawings.